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Updated Forecast of Atlantic Seasonal Hurricane Activity

Today, Dr. Phil Klotzbach and Dr. Bill Gray released their updated forecast for the 2009 Atlantic hurricane season. They are calling for a below-average season with ten named storms, four of which will become hurricanes, and two becoming major (Category 3, 4 or 5) hurricanes. The reduced numbers from their early June forecast are due largely to the development of an El Niño.

They state that their early August statistical forecast methodology shows strong evidence over more than 100 past years that significant improvement over climatology can be attained. Their forecasts are issued to satisfy the curiosity of the general public and to bring attention to the hurricane problem.

Bill Gray gets the credit for pioneering these seasonal forecasts and has been issuing them for 26 years. Phil Klotzbach joined Bill’s team in 2000 and has been the lead on the seasonal forecasting team since 2006. You can see today’s forecast as well as past forecasts and verifications at http://hurricane.atmos.colostate.edu/Forecasts.

Today’s forecast of below-average activity in the Atlantic is welcome news. But it is extremely important to note their statement on page 2 of the report: “… all coastal residents should prepare for the coming hurricane season every year, since landfalling tropical cyclones can devastate communities in inactive or active seasons. It only takes one landfalling system to make this a very active season for you.” And I applaud them for making it clear that “…these seasonal forecasts are based on statistical schemes which, owing to their intrinsically probabilistic nature, will fail in some years. Moreover, these forecasts do not specifically predict where within the Atlantic basin these storms will strike.” It is important for people to understand that. Preparedness efforts should continue no matter what the seasonal forecasts call for.

Phil and Bill agree with NOAA that the El Niño that has developed over the past couple of months will likely intensify to a moderate El Niño over the next few months. El Niño events tend to be associated with increased levels of vertical wind shear and decreased levels of Atlantic hurricane activity.

“Although we have been in an active multi-decadal Atlantic Basin hurricane era since 1995, it is not unusual to have a few below-average years within an active multi-decadal period.” That’s the good news. The bad news is that Phil and Bill “expect the active Atlantic hurricane era that we have been in since 1995 to continue for the next 10-15 years.”

They are planning on issuing experimental 15-day forecasts approximately every two weeks during the peak August-October period.